Not applicable.
1. Field of the Invention
The present invention relates to the field of dispensing systems. More specifically, the present invention relates to the field of systems for dispensing viscous fluids onto a substrate.
2. Description of Related Art
Dispensing systems are used in the manufacture of a variety of articles including electronics, motherboards, microprocessors and liquid crystal displays. Typically, a dispensing system consists of a stationary surface, a dispenser for dispensing a substance onto the surface, and a servo mechanism for controlling the movement of the dispenser. The surface generally contains a substrate that acts to receive the substance that is deposited by the dispenser. The dispenser can deposit a variety of substances including viscous materials such as glue or an elastomer. The dispenser is moved over the substrate by a servo device as the dispenser deposits a substance onto the substrate. The substance deposited on the substrate can later be cured by thermal means.
In the manufacture of certain products, such as a liquid crystal display, it is necessary to fasten together two substrates usually with a glue sealant in conjunction with a substance such as an elastomer. In addition, it is necessary for the two substrates to maintain a particular distance constantly between them. The distance between the two substrates is dictated by the thickness of the substance, usually the glue sealant and the spacer balls, sealing the two substrates. When using a dispenser to deposit a viscous material, the height at which the dispenser deposits the substance onto the substrate can affect the thickness of the substance on the substrate. Thus, when a dispenser is used to deposit a substance for sealing together two substrates that must be kept at a particular distance from each other, it is necessary that the dispenser is kept at a particular height over the surface as the dispenser moves over it. This is a difficult task as the distance between the dispenser and the substrate is typically very smallxe2x80x94on the order of microns. Also, inadvertent movements of the surface beneath the dispenser can add an additional obstacle in maintaining a constant distance between the dispenser and the substrate. In addition, the movement of the dispenser by the servo device can add an additional obstacle in maintaining a constant distance.
Accordingly, what is needed is a method and system that effectively maintains the dispenser at a desired distance from the surface.
Briefly, in accordance with the present invention, disclosed is a system and method for maintaining a dispensing system a desired distance between a dispenser and a surface. In an embodiment of the present invention, the system includes a light-emitting device, connected to the dispenser, that emits light in the direction of the surface. The emitted light is reflected off of the surface as well as a mirror connected to the dispenser. Subsequently, all reflected light is received by a sensor. Using the sensor data and measuring interference fringes, a computer calculates the distance between the dispenser and the surface. A servo device then adjusts the location of the dispenser, in accordance with the calculated distance, in order to maintain the desired distance between the dispenser and the surface.
In another embodiment of the present invention, the system includes a first conductive element attached to the dispenser and a second conductive element attached to the surface. A voltage is applied to both conductive elements, which form a capacitor. Then, a sensor or bridge circuit measures the capacitance between the two conductive elements. Using the sensor data, a computer calculates the distance between the dispenser and the surface. A servo device then adjusts the location of the dispenser, in accordance with the calculated distance, in order to maintain the desired distance between the dispenser and the surface.
In another embodiment of the present invention, the system includes a spring attached to the dispenser. The spring is made to contact the surface, which produces a restoring force within the spring. Then, a sensor measures the restoring force of the spring. Using the sensor data, a computer calculates the distance between the dispenser and the surface. A servo device then adjusts the location of the dispenser, in accordance with the calculated distance, in order to maintain the desired distance between the dispenser and the surface. In another embodiment of the present invention, the system includes a spring and a light-emitting device, both of which are attached to the dispenser. The spring is made to contact the surface, which produces a restoring force within the spring. The light-emitting device emits light that is reflected off of the spring. A sensor receives the light reflected off of the spring. Using the sensor data, a computer calculates the distance between the dispenser and the surface. A servo device then adjusts the location of the dispenser, in accordance with the calculated distance, in order to maintain the desired distance between the dispenser and the surface.
One advantage of the present invention is the increased ability to quickly and efficiently detect and modify the distance between the dispenser and the surface. This allows a dispenser to maintain a desired distance between the dispenser and the surface. This can lead to the production of a higher quality product by a dispensing system. This can also lead to increased production by a dispensing system.
The foregoing and other features and advantages of the present invention will be apparent from the following more particular description of the preferred embodiments of the invention, as illustrated in the accompanying drawings.